CHICAGO (AP) -- A United Airlines spokesman says airline employees were "following the right procedures" when they called police who then dragged a man off a plane at Chicago's O'Hare International Airport.

Charles Hobart says the employees were justified in calling law enforcement Sunday night to remove the man because the flight was overbooked and couldn't leave for Louisville, Kentucky, with too many passengers on board.

He said in an email that United employees had asked for volunteers and when none were forthcoming, four were selected to leave.

A video shot by another passenger shows the man being pulled across a seat and armrest and physically dragged from the plane.

Hobart says the man was removed by Chicago police but the police department says its officers were not involved. Officer Jose Estrada says the incident was handled by the city's aviation department police force.